The National Surgical Adjuvant Breast and Bowel Project (NSABP) is an NCI-- funded clinical cooperative group that has conducted large-scale clinical trials evaluating therapies in the treatment of primary breast and bowel cancer. Procedures have been implemented across all trials to 1) minimize ineligibility rates, 2) allow central pathology review of all patients, 3) maintain good follow-up reporting with low data-delinquency rates, and 4) provide ongoing medical review of protocol compliance. The results of two NSABP trials in the adjuvant treatment of node-negative breast cancer have demonstrated an improved disease-free survival; however, all node-negative patients do not benefit from adjuvant therapy, and "better" markers are needed to more accurately identify those individuals who should receive a particular therapy. Although numerous markers have been reported to be of value in such an effort, none have been evaluated and compared with established markers or with newer markers in the same population of patients. This proposal will allow for the retrieval of tumor specimens by the investigators from patients entered into these two NSABP trials. Once these specimens are obtained, the determination of multiple new markers will be possible in this well-controlled, carefully characterized, prospectively followed patient population. The analysis of marker results with patient outcome would be performed independently of the marker determinations.